Ferrule type renewable cartridge fuse



Feb. 19, 1957 DETCH ,782,286

FERRULE TYPE RENEWABLE CARTRIDGE FUSE Filed Feb. 17, 1953 2 Sheets-Sheet2 FlGJg FIGJ4 FIGJ5 FIGJG ITF --63 XI: f T 54- IN V EN TOR.

"/(MSM ATTORNE Y United States Patent 2,782,286 FERRULE TYPE RENEWABLECARTRIDGE FUSE A" Lewis Detch, Pittsburgh, Pa.

Application February 17, 1953, Serial No. 337,357

" 9 Claims. (Cl. 200-131 This invention relates to electric circuitbreakers, particularly thermal current breakers and more especiallyfusible element breakers of the well knownferrule type renewablecartridge fuse form.

Those acquainted with well known ferrule type cartridge electric fusesare well aware that known forms are so constructed that the electricalconnection between the interior fusible link and the metallic'endferrules is such that considerable wasteful and deleterious heat isgenerated. They further known that this wasteful heat is soinefficiently dissipated that the horn fibre cartridge is slowlycarbonized and often ultimately destroyed by this heat. They also knowthat upon thermal destruction of the fusible element, the hot metal,vapors and gases are so inefiiciently conducted to the outside of thefuse that the horn fibre cartridge is subjected for so long a time tothese products that it is carbonized and often ultimately destroyed and,in addition, nearby inflammable materials are often subjected to a heatquite sufiicient to ignite them. Furthermore the several metal parts atthe ends of the fuse are frequently soldered firmly together by thevaporized metal, upon cooling, so that it is often difiicult todisassemble the fuse after destruction of the fusible element therein.

It is also well known that the usual types of ferrule cartridge fusesare so constructed that a thoroughly efiicicnt electrical contact of lowohmic resistance between the several current carrying parts of apermanent, lasting and uniform nature is not obtained.

It is further known that the time lag of blowing or thermal destructionof the fusible link is decreased in known forms of ferrule typecartridge fuses by reason of the lack of proper and firm and lastingconnections and lack of heat reservoirs or heat absorbers of sufficientthermal capacity at the several ends of the fuse, and as a consequence,a greater portion of the fusible link is destroyed upon blowing therebyincreasing the deleterious effects caused by hot metal, vapors, andgases.

A principal object of this invention is to provide a' fuse of the typespecified that, compared to present well known forms: develops lesswasteful heat during the ordi-' nary passage of current therethrough;dissipates more efficiently any such wasteful heat that may begenerated;

efficiently absorbs the heat of hot metal, vapors and gases formed whenthermal destruction of the fusibleelement occurs, so-that adjacentinflammable materials are not so readily ignited and closely adjacentparts of the fuse arenot so readily soldered-together; and by-reason ofthe less generation of wasteful heat and the more efiicient dissipationof wasteful heat generated and the heat gen-i erated when thermaldestruction of the fuse element occurs, the cartridge'shell of thefuseisless' subjected to carbonization and'destruction and so has a longerlife.

A further object of the invention is to provide a fuse of the typespecified comprising relatively few partsjeasily and inexpensivelyconstructed and easilyand quicklyassembled, jso formed and related that,as compar'edto Y "ice well known forms, such lasting firm contact isreadily obtained between metal current carrying members that relativelylittle wasteful ohmic resistance is introduced into a circuit of whichthe fuse forms a part.

A further object of the invention is to provide a fuse of the typespecified which is so constructed that with a given fusible element itwill give a longer time lag than the same given fusible element willwhen installed in well known forms.

A further object of the invention is to provide a fuse of the typespecified which will be so constructed that, upon thermal destruction ofthe fusible element, less of the fusible element will be volatilizedthan in well known fuses of like rated capacity.

A further object of the invention is to provide a fuse of the typespecified which will be so constructed that the ends thereof will be soclosed that hot metal, vapors and gases generated upon thermaldestruction of the fusible element will be forced to come in contactwith a substantial body of heat absorbable metal before flowing into theouter air whereby superior cooling will be effectuated.

A further object of the invention is to provide a fuse of the typespecified which will be so constructed that the usual clamping of thebent over end of the fusible element will ensure a superior broader areainitial electrical contact between the end of the fusible element andthe usual.

ferrule, and so a lower ohmic resistance, and also a superior mechanicalclamp of a more permanent nature, so designed that the fusible elementwill not be twisted when the usual ferrule is tightened, said mechanicalclamp being of greater mechanical permanence, effectiveness anduniformity in application and operation and of greater ease of assemblythan known types.

A further object of the invention is to provide a fuse of the typespecified which will provide means by which it may be more readilymanually disassembled without the use of tools.

Other objects and advantages will appear as the description of theparticular physical embodiment selected to illustrate the inventionprogresses and the novel features will be particularly pointed out inthe appended claims.

In describing the invention in detail and the particular physicalembodiment selected to illustrate the invention, reference will be hadtothe accompanying drawings and the several views thereon, in which, likecharacters of reference designate like parts throughout the severalviews, and in which:

Fig. l is a plan view of a ferrule type renewable cartridge fuse of myinvention;

Fig. 2 is a longitudinal sectional view of the device as shown by Fig.1;

Fig. 3 is a longitudinal sectional view of the device, as shown by Fig.1, taken at an angle of 90 from the plane upon which the view, Fig. 2,is taken;

Fig. 4 is a face view of a plug or fusible element retaining member usedin my invention;

Fig. 5 is a cross sectional view of the device as shown by Fig. 4;

Fig. 6 is a view of the device as shown by Fig. 4 as viewed from the endopposite to that from which Fig. 4

is viewed;

Fig. 7 is a fragmentary sectional view illustrating a modified form offuse terminal construction embodying my invention;

Fig. 8 is across sectional view of the device, as shown by Fig. 7, onthe plane indicated by the line VIlIVIII of Fig. 7 viewed in thedirection of the arrows at the ends of the line;

Fig. is a fragmentary sectional view of a further modified form of fuseend construction embodying my invention;

Fig. 11 is a cross sectional View of the device as shown by Fig. 10 onthe plane indicated by the line Xi-Xl, viewed in the direction of thearrows at the ends of the line;

Fig. 12 is a rear or inner end view of the plug or fusible elementretaining member as shown in Fig. 10;

Fig. 13 is a fragmentary sectional view of a modified fuse endconstruction of my invention;

Fig. 14 is a face or outer end view of the fusible element retainingmember as shown in the device as shown by Fig. 13;

Fig. 15 is a cross sectional view of the fusible element retainingmember, as shown in Fig. 13, on the plane indicated by the line XV-XVviewed in the direction of the arrows at the ends of the line;

Fig. 16 is a rear or inner end view of the fusible element retainingmember illustrated in Fig. 13;

Fig. 17 is a fragmentary sectional view illustrating a further modifiedfuse end construction of my invention;

Fig. 18 is an outer or face view of the fusible element retaining memberillustrated in Fig. 17;

Fig. 19 is a cross sectional view corresponding to the cross sectionalview Fig. 15 but of the fusible element retaining member shown in Fig.17; and

Fig. 20 is a rear or inner end view of the fusible element: retainingmember shown in Fig. 17.

Fig. 1 illustrates a common and well known form of ferrule ty ecartridge renewable fuse, in-so-far as outward appearance is concerned,with one exception, and that is the knurling 1.

The device as shown by Figs. 1 to 3 inclusive includes an elongatedhollow cylinder formed of insulating material, preferably horn fibre andopen at each end.

The cylinder 2 serves to enclose a fusible element 7 of any of the usualforms and made of any usual material, such as zinc or aluminum or analloy thereof.

The fusible link 7 is connected to the external circuit by interiormetallic members and exterior metallic ferrules, caps or outer closingmembers, one at each end, and designated 3. These metallic caps or endpieces are preferably made of brass and in the particular form shown inFig. 2 are hollow cylinders with a side wall in which an internal screwthread 4- is formed and with a single end Wall 5 formed with a nub orprotuberance 6 projecting inwardly from the inner face. Said end wall 5closes the respective end of the collar 10 and cylinder 2.

The insulating tube 2, preferably, and in the form shown in Fig. 2, hasreduced portions at each end as 8. These reduced portions accommodatemetallic collars 10, open at each of their ends, preferably made ofbrass and preferably force fitted into place on the ends of the tube 2so as to be fixed relative thereto. These collars, in the form shown in2, are provided with an external screw thread 12 matching and adapted tocooperate with the screw thread 4 of the caps 3. These collars 10 in theform shown in Fig. 2 are provided with radially inwardly extendingportions 14, and these inwardly extending portions 14 preferably abutthe ends of the tube 2.

At each end of the tube 2 a fusible element retaining member 16 isprovided. This feasible element retaining member or substantiallycylindrical, solid and massive plug is formed of metal, preferablybrass, and as well shown in Figs. 4 to 6 inclusive, includes a bodyportion 18 which is slightly tapered and a radially outwardly extendingflange portion 20. It is also provided with a through slot 22 andcentrally located in the outer end face 24 there is formed a cup shapedor inwardly diminishing frusto conical depression 26. As best shown byreference to Fig. 6, the plug 16 may also be provided with vents as 28,30, 32 and 34. Two of these, and. 34, extend from the tapered portion 18to the outerperiphery ofthe enlarged portion 20. The outer two vents, 28and 32, extend from the slot 22 to the outer periphery of the enlargedportion 20.

As will be seen by reference to Figs. 2 and 3, the fusible link 7 hasits ends passing through the slots, as 22, and protruding to some extentbeyond the outer face of the plug 16. These protruding ends are eachbent down into the plane of the outer face of the plug 16 and then whenthe cap or ferrule 3 is tightened by being screwed down into place, thenub or protuberance 6 forces the bent-over end of the fusible elementinto the depression 26, and thus not only secures an inward electricalcontact of superior broader area, but also a more permanent electricalcontact than is usual in fuses of this type, because the end of thefusible element is forced into a cup shape into the frusto conicaldepression 26 of the plug 1.6. The end portion 7A in fact assumes afrusto conical shape tightly clamped in and tightly fitting in the saiddepression 26, as the diameter of protuberance 6 is slightly less thanthe lesser diameter of the depression 26. Said lesser diameter isroughly one third the greatest diameter of plug 16.

In the usual type of well known fuses, when the cap 3 is screwed in.place, and the turned over end of the fusible link is pressed againstthe fusible link retaining member, which is, in the well known form,merely a pierced washer resting on the end of the insulating cylinder orcollar, the twisting movement of the cap is imparted to the link and tothe washer, and both are frequently turned or twisted to such an extentthat the fusible link is damaged by tearing and sometimes by actualdestruction. By my construction, however, this is avoided. The plug 16has a tapered body 18 and this taper just fits tightly between theinwardly extending portions 14 of the collar. This plug fits so tightlythat the twisting movement of the cap will not cause it to turn. Thetwisting and perhaps injury or destruction of the fusible element 7 isthus entirely avoided.

The plug 16 is of metal and is of quite a substantial body. It has athermal capacity probably greater than three or four of the usualwashers commonly employed in well known types of ferrule fuses. Itslength is approximately half of its greatest diameter. By reason of thissubstantial heat absorbing body of considerable thermal capacity, anyheat which may be generated when the fuse is inserted in a circuit, isreadily absorbed and transmitted to the collar 10 and the ferrule 3 andso to the outer atmosphere. Due to this ready absorption of heat by theplug 16, the interior surface of the tube 2 does not become so highlyheated and so is not so readily carbonized and perhaps destroyed. Thenet result of the construction is that the cylinder 2 lasts aconsiderably longer time.

Not only does the large thermal capacity body 16 keep the insulatingtube 2 cooler, but it also has a decided etfect upon the functioning ofthe fusible element 7. As it extends a much greater distance along thefusible element 7 than does the ordinary and well known washer form offusible element retainer, it keeps the fusible element cooler than itwould otherwise be so that when an excessive current tends to flowthrough the fusible element, the fusible element is at a lowertemperature than in well known forms of fuses and consequently itrequires a greater time to heat the fusible element up to the melting ordestruction point. This is very advantageous as it increases the timelag of blowing or destruction of the fuse when an excessive currentoccurs, so that at times, if the excessive current is not too great, thefuse will withstand it, and there will arise no necessity to renew thelink.-

In summation, the link 7 is in tight electrically conductive and heattransfer relation with the plug 16 and end piece 3, and the plug is intight electrical and heat transfer relation with the collar 10 and thuswith the end piece. The elements 3, 7, 10 and 16 thus related becomeelectrically and thermally almost a single massof metal. Each element isitself a single or unitary piece of metal, and each is in-tight contactwith two others. In any given split second, half of the heat of portion7A will transfer to nub 6 and be disssipated by the exterior surfaces ofpiece 3, while the remainder will be quickly absorbed by the massiveplug 16 and transfer through surface 18A and flange 20 to collar 10 andthus to the piece 3. At the first two points of transfer the portion 7Ais deformed, brightened and clamped, and heat transfer is facilitated tothe exterior piece 3 and to the massive plug 16.

When the link 7, enclosed in a fuse of my invention, does actually blowor become thermally destroyed, and the molten metal, hot vapors and heatgases are generated within the tube 2, they are obliged to flow alongthe outer surface of the tapered portion of the plug 16, that is, alongthe tapered surface 18A, and also through the slot 22 where they areincontact with a very extensive coo-ling surface, so that before the hotmaterial generated by the destruction of the fusible element is inposition to pass out from the fuse down through and along thecooperating threads 4 and 12 of the collar 10 and the cap or outerclosing member 3, they have been so quite thoroughly cooled that uponissuing they are not of suflicient temperature to readily ignite closelyadjacent inflammable material and are so cool by the time they reach thecooperating thread between the collar and the cap or outer closingmember that they have no great tendency to solder the threads together.-

After the hot metal, and vapors and gases pass the contact between theplug 16 and the inwardly projecting members 14 of the collar, I providea somewhat freer path by reason of the venting of channels and 34 whichextend radially across the inner face 20A of the flange portion 20. Ideem it preferable to provide supplementary venting channels 28 and 32between the slots 22 and the outer periphery of the enlarged or flangeportion of the plug.

The hot metal, vapor and gases are not only cooled by the plug 16, butthose materials of destruction which pass up through the slot 22 alsoexpand into the space between the plug 16 and the inner face of the endwall of the cap or outer closing member 2 and are thereby quite wellcooled before issuing through the cooperating thread between the cap 3and the collar 10.

The fusible element retaining member or plug 16 has' a portion of itsperiphery, that is, the enlarged or flange portion 20 which abuts thesleeve 10, scored as by knurling. This scoring or knurling serves twopurposes, one, it effectually breaks up the direct flow of gasestherepast which have flowed through the slot 22 whereby hot metal may bedeposited on the knurling and, two, it provides a means whereby the plugmay be removed from its position in the fuse especially when it has beenjammed down tightly into the space provided by the inwardly extendingportions of the collar 10.

As my fuse is so constructed that soldering of the parts together isavoided, there is really no necessity for the use of tools to open thefuse aftera blow. I may provide slots ,as 36 to facilitate the use of ascrew driver inremoving the outer closing member or cap 3, but I preferto 'knurla small portion, as 1, of the cap, so that a manual grip may beobtained on the caps sufficient to enable one to remove the cap withoutthe use of tools, thereby greatly facilitating and hastening the renewalof the fusible link after the fuse has blown.

In Fig. 7 I have shown a fragment of the terminal portion of the fuse inwhich the outer closing member or cap 3 is of the type previouslydescribed and the collar 38 is formed with depressed portions as 40 and42 to cooperate with projections as 44 and 46 on the plug 48. Thesecooperating depressions and projections serve to prevent relativerotation between the plug and the collar.

The fragmentary view, Fig. 10, shows a terminal construction in whichthe collar 50, is formed with an internal thread 52 and the portioncorresponding to the outer cap 3 of Figs. 1 to 6 inclusive is replacedby a disc member 54 which is provided with an external thread 56.

The plug 58 of Figs. 10, 11 and 12 is formed with a slot 60 which opensin the side periphery of the plug as at 62.

The fragmentary showing, Fig. 13, illustrates a terminal construction ofthe fuse in which the fusible link retaining member 64 is formed with adepending polygonal projection 66 to fit into a corresponding polygonalopening formed in the inwardly extending portion 68 of the collar 70.This construction effectually prevents rotation of the fusible linkretaining member relative to the collar 70.

Fig. 17 illustrates a terminal construction of a fuse in which thefusible link retaining member 72 is made identically on both sidesthereof, that is, there is a circular depression 74 on one side thereofand a corresponding circular depression 76 on the other side thereof, sothat the fusible link retaining member 72 may be used either sideoutwardly.

It is to be understood that the various modifications may beusedinterchangeably in fuses, for instance, I do not mean to exclude the useof a collar, as 50, with a portion projecting above the inwardlyextending portion with a cap such as 3.

Although I have particularly described a particular preferred form of myinvention and various modifications thereof, nevertheless, I desire tohave it understood that the forms selected are merely illustrative, butdo not exhaust the possible physical embodiments of the idea of meansunderlying my invention.

What -I claim as new and desire to secure by Letters Patent is:

1. In a cartridge fuse having an elongated hollow cylinder open at bothends formed of electrical insulating material, a fusible link within thecylinder, a metallic collar on each end formed with external screwthreads, and an outer closing member on each end formed with screwthreads mating and cooperating with the screw threads of the collar, theinvention comprising -a fusible link retaining member resting on eachcollar and closing the end of the cylinder, said fusible link retainingmember formed with a slot for passing the end of the fusible link in thecylinder therethrough with the end of the fusible link protruding, saidfusible link retaining member also formed on its outer face with acentral depression, said outer closing member formed with a nubpositioned to cooperate with the central circular depression in the faceof the fusible link retaining member whereby the protruding end of thefusible link may be bent down and be held firmly by the nub in thecircular depression, said fusible link retaining member further "beingformed with a venting slot connecting said first mentioned slot with theperiphery of said retaining member. I

2. In an electrical fuse of the type comprising an insulatingcylindrical shell open at each end, conductive collars mounted at eachend of said shell, said collars being open at each of their ends, endpieces threadedly engaging said collars and closing the outer endsthereof, slotted fuse link retaining members held between said collarsand said end pieces and a fusible link extending through the slots ofboth of said retaining members and having its end portions bent over andclamped between said retaining members and said end pieces, theimprovement comprising said retaining members each having an outer endface formed with a cup shaped central depression and said end pieceseach being formed with an inward extending circular protuberance whichupon tightening of said end piece forces the bent over end portion ofsaid link into tightly clamped cup shape, said collars further having attheir outer ends radially inwardly extending portions, said retainingmembers further having at their outer ends outwardly extending flangesabutting said inwardly extending portions of said collars, said flangesfurther having inner faces formed with vent slots extending thereacross.

3. In an electrical fuse of the type comprising an insulatingcylindrical shell open at each end, conductive collars mounted at eachend of said shell, said collars being open at each of their ends, endpieces threadedly engaging said collars and closing the outer endsthereof, slotted fuse link retaining members held between said collarsand said end pieces and a fusible link extending through the slots ofboth of said retaining members and having its end portions bent over andclamped between said retaining members and said end pieces, theimprovement comprising said retaining members each having an outer endface formed with a cup shaped central depression and said end pieceseach being formed with an inward extending circular protuberance whichupon tightening of said end piece forces the bent over end portion ofsaid link into tightly clamped cup shape, said collars further having attheir outer ends radially inwardly extending portions, said retainingmembers further having at their outer ends outwardly extending flangesabutting said inwardly extending portions of said collars, said flangesfurther having inner faces formed with vent slots extending from saidlink slots to the periphery of said flanges.

4. In an electrical fuse of the type comprising an insulatingcylindrical shell open at each end, conductive collars mounted at eachend of said shell, said collars being open at each of their ends, endpieces threadedly engaging said collars and closing the outer endsthereof, slotted fuse link retaining members held between said collarsand said end pieces and a fusible link extending through the slots ofboth of said retaining members and having its end portions bent over andclamped between said retaining members and said end pieces, theimprovement comprising said retaining members each having an outer endface formed with a cup shaped central depression and said end pieceseach being formed with an in- Ward extending circular protuberance whichupon tightening of said end piece forces the bent over end portion ofsaid link into tightly clamped cup shape, said retaining members furtherhaving flanges abutting portions of said collars, said flanges havingknurled peripheries for the cooling of gases escaping therepast.

5. In a cartridge fuse having an elongated hollow cylin der open at bothends formed of. electrical insulating mate rial, a fusible link Withinthe cylinder, a metallic collar on each end formed with screw threads,and an outer closing member. on each end formed with screw threadsmating and cooperating with the screw threads of the collar, theinvention comprising a fusible link retaining member resting on eachcollar and closing the end of the cylinder, said fusible link retainingmember formed with a slot for passing the end of the fusible link in thecylinder therethrough with the end of the fusible link protruding, saidfusible link'retain'ing member also formed on its outer face with acentral depression, said outer closing member formed with a nubpositioned to cooperate with the central circular depression in the faceof the fusible link retaining member whereby the protruding end of'thefusible link may be bent down and be held firmly by the nub in thecircular depression, said fusible link retaining member further beingformed with a venting slot connecting said first mentioned slot with theperiphery of said retaining member.

6. In a cartridge fuse having an elongated hollow cylinder of insulatingmaterial open at both ends, a fusible link within the cylinder,retaining means slotted to receive an end portion of said fuse link anda conductive and heat absorbing end piece clamping a bent over endportion of said fuse link against said retaining means, the improvementcomprising a conductive and heat absorbing metallic collar fixedlymounted at an end of said cylinder and having screw threads, saidretaining means being a substantially solid and massive body ofconductive and heat absorbing material, said body being substantiallycylindrical and having a length approximately half its largest diameter,said body further having an outer end face formed with a centraldepression, said end portion of said fusible link extending across saiddepression, said end piece further being formed with threads engagingthe threads of said collar, said end piece further having a centralcircular protuberance extending inwardly therefrom, said protuberanceupon tightening of the threads of said collar and of said end piecedeforming said end portion of said fusible link into said depression andtightly clamping the same therein in electrically conductive and heattransferring relation, said retaining means further fitting in andtightly contacting said collar in electrically conductive and heattransferring relation.

7. A cartridge fuse according to claim 6, said protuberance furtherbeing an integral portion of said end piece.

8. A cartridge fuse according to claim 6, said depression being inwardlydiminishing fmsto-conical and its smaller diameter being substantiallyone third the largest diameter of said retaining means.

9. A cartridge fuse according to claim 6, said retaining means furtherhaving a tapered side surface and said side surface being a portionthereof which tightly fits in and contacts said collar.

References Cited in the file of this patent UNITED STATES PATENTS994,413 Mallory June 6, 1911 1,102,981 Daum July 7, 1914 1,443,887 Sandset al. Jan. 30, 1923 1,473,615 Folds Nov. 13, 1923 1,478,109 EllisonDec. 18, 1923 1,502,883 Sandin July 29, 1924 1,700,080 Sandin Jan. 22,1929 1,857,096 Glowacki May 3, 1932 1,881,369 Carney M Oct. 4, 19321,953,011 Cote Mar. 27, 1934 1,968,763 Hanson et al July 31, 19342,071,843 Korn Feb. 23, 1937 2,168,153 Brown Aug. 1, 1939 2,449,827 VonHoorn Sept. 21, 1948 2,522,473 Vischer Sept. 12, 1950

